In MyDbs Class we created a class that opens and closes databases for us. We now make use of that class to load inventory data into two databases that we will use for our inventory system.
Again, remember that you can find the complete implementation for these functions in:
DB_INSTALL/examples_java/db/GettingStarted
where DB_INSTALL
is the location where you
placed your DB distribution.
Note that in this example, we are going to save two types of information. First there are a series of inventory records that identify information about some food items (fruits, vegetables, and desserts). These records identify particulars about each item such as the vendor that the item can be obtained from, how much the vendor has in stock, the price per unit, and so forth.
We also want to manage vendor contact information, such as the vendor's address and phone number, the sales representative's name and his phone number, and so forth.
Example 8.1 Inventory.java
All Inventory data is encapsulated in an instance of the following
class. Note that because this class is not serializable, we need a
custom tuple binding in order to place it on a DatabaseEntry
object. Because the TupleInput
and
TupleOutput
classes used by custom tuple bindings
support Java numerical types and not Java numerical classes, we use
int
and float
here instead of the
corresponding Integer
and Float
classes.
// File Inventory.java package db.GettingStarted; public class Inventory { private String sku; private String itemName; private String category; private String vendor; private int vendorInventory; private float vendorPrice; public void setSku(String data) { sku = data; } public void setItemName(String data) { itemName = data; } public void setCategory(String data) { category = data; } public void setVendorInventory(int data) { vendorInventory = data; } public void setVendor(String data) { vendor = data; } public void setVendorPrice(float data) { vendorPrice = data; } public String getSku() { return sku; } public String getItemName() { return itemName; } public String getCategory() { return category; } public int getVendorInventory() { return vendorInventory; } public String getVendor() { return vendor; } public float getVendorPrice() { return vendorPrice; } }
Example 8.2 Vendor.java
The data for vendor records are stored in instances of the following class. Notice that we are using serialization with this class for no other reason than to demonstrate serializing a class instance.
// File Vendor.java package db.GettingStarted; import java.io.Serializable; public class Vendor implements Serializable { private String repName; private String address; private String city; private String state; private String zipcode; private String bizPhoneNumber; private String repPhoneNumber; private String vendor; public void setRepName(String data) { repName = data; } public void setAddress(String data) { address = data; } public void setCity(String data) { city = data; } public void setState(String data) { state = data; } public void setZipcode(String data) { zipcode = data; } public void setBusinessPhoneNumber(String data) { bizPhoneNumber = data; } public void setRepPhoneNumber(String data) { repPhoneNumber = data; } public void setVendorName(String data) { vendor = data; } ... // Corresponding getter methods omitted for brevity. // See examples/je/gettingStarted/Vendor.java // for a complete implementation of this class. }
Because we will not be using serialization to convert our
Inventory
objects to a DatabaseEntry
object, we need a custom tuple binding:
Example 8.3 InventoryBinding.java
// File InventoryBinding.java package db.GettingStarted; import com.sleepycat.bind.tuple.TupleBinding; import com.sleepycat.bind.tuple.TupleInput; import com.sleepycat.bind.tuple.TupleOutput; public class InventoryBinding extends TupleBinding { // Implement this abstract method. Used to convert // a DatabaseEntry to an Inventory object. public Object entryToObject(TupleInput ti) { String sku = ti.readString(); String itemName = ti.readString(); String category = ti.readString(); String vendor = ti.readString(); int vendorInventory = ti.readInt(); float vendorPrice = ti.readFloat(); Inventory inventory = new Inventory(); inventory.setSku(sku); inventory.setItemName(itemName); inventory.setCategory(category); inventory.setVendor(vendor); inventory.setVendorInventory(vendorInventory); inventory.setVendorPrice(vendorPrice); return inventory; } // Implement this abstract method. Used to convert a // Inventory object to a DatabaseEntry object. public void objectToEntry(Object object, TupleOutput to) { Inventory inventory = (Inventory)object; to.writeString(inventory.getSku()); to.writeString(inventory.getItemName()); to.writeString(inventory.getCategory()); to.writeString(inventory.getVendor()); to.writeInt(inventory.getVendorInventory()); to.writeFloat(inventory.getVendorPrice()); } }
In order to store the data identified above, we write the
ExampleDatabaseLoad
application. This application
loads the inventory and vendor databases for you.
Inventory information is stored in a Database
dedicated for that purpose. The key for each such record is a product
SKU. The inventory data stored in this database are objects of the
Inventory
class (see Inventory.java for more information).
ExampleDatabaseLoad
loads the inventory database
as follows:
Reads the inventory data from a flat text file prepared in advance for this purpose.
Uses java.lang.String
to create a key based
on the item's SKU.
Uses an Inventory
class instance for the
record data. This object is stored on a DatabaseEntry
object using InventoryBinding
, a custom tuple
binding that we implemented above.
Saves each record to the inventory database.
Vendor information is also stored in a Database
dedicated for that purpose. The vendor data stored in this database are objects of the
Vendor
class (see Vendor.java for more information). To load this
Database
, ExampleDatabaseLoad
does the following:
Reads the vendor data from a flat text file prepared in advance for this purpose.
Uses the vendor's name as the record's key.
Uses a Vendor
class instance for the
record data. This object is stored on a DatabaseEntry
object using com.sleepycat.bind.serial.SerialBinding
.
Example 8.4 Stored Class Catalog Management with MyDbs
Before we can write ExampleDatabaseLoad
, we need to update
MyDbs.java
to support the class catalogs that we need for this application.
To do this, we start by importing an additional class to support stored class catalogs:
// File: MyDbs.java
package db.GettingStarted;
import com.sleepycat.bind.serial.StoredClassCatalog;
import com.sleepycat.db.Database;
import com.sleepycat.db.DatabaseConfig;
import com.sleepycat.db.DatabaseException;
import com.sleepycat.db.DatabaseType;
import java.io.FileNotFoundException;
We also need to add two additional private data members to this class. One supports the database used for the class catalog, and the other is used as a handle for the class catalog itself.
public class MyDbs { // The databases that our application uses private Database vendorDb = null; private Database inventoryDb = null;private Database classCatalogDb = null; // Needed for object serialization private StoredClassCatalog classCatalog;
private String vendordb = "VendorDB.db"; private String inventorydb = "InventoryDB.db";private String classcatalogdb = "ClassCatalogDB.db";
// Our constructor does nothing public MyDbs() {}
Next we need to update the MyDbs.setup()
method
to open the class catalog database and create the class catalog.
// The setup() method opens all our databases
// for us.
public void setup(String databasesHome)
throws DatabaseException {
DatabaseConfig myDbConfig = new DatabaseConfig();
...
// Database configuration omitted for brevity
...
// Now open, or create and open, our databases
// Open the vendors and inventory databases
try {
vendordb = databasesHome + "/" + vendordb;
vendorDb = new Database(vendordb,
null,
myDbConfig);
inventorydb = databasesHome + "/" + inventorydb;
inventoryDb = new Database(inventorydb,
null,
myDbConfig);
// Open the class catalog db. This is used to
// optimize class serialization.
classcatalogdb = databasesHome + "/" + classcatalogdb;
classCatalogDb = new Database(classcatalogdb,
null,
myDbConfig);
} catch(FileNotFoundException fnfe) {
System.err.println("MyDbs: " + fnfe.toString());
System.exit(-1);
}
}
Finally we need a getter method to return the class catalog. Note that we do not provide a getter for the catalog database itself – our application has no need for that.
We also update our close()
to close our class catalog.
// getter methods
public Database getVendorDB() {
return vendorDb;
}
public Database getInventoryDB() {
return inventoryDb;
}
public StoredClassCatalog getClassCatalog() {
return classCatalog;
}
Finally, we need our close()
method:
// Close the databases
public void close() {
try {
if (vendorDb != null) {
vendorDb.close();
}
if (inventoryDb != null) {
inventoryDb.close();
}
if (classCatalogDb != null) {
classCatalogDb.close();
}
} catch(DatabaseException dbe) {
System.err.println("Error closing MyDbs: " +
dbe.toString());
System.exit(-1);
}
}
}
So far we have identified the data that we want to store in our
databases and how we will convert that data in and out of
DatabaseEntry
objects for database storage. We
have also updated MyDbs
to manage our databases
for us. Now we write ExampleDatabaseLoad
to
actually put the inventory and vendor data into their respective
databases. Because of the work that we have done so far, this
application is actually fairly simple to write.
Example 8.5 ExampleDatabaseLoad.java
First we need the usual series of import statements:
// File: ExampleDatabaseLoad.java package db.GettingStarted; import java.io.BufferedReader; import java.io.File; import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.IOException; import java.io.InputStreamReader; import java.util.ArrayList; import java.util.List; import com.sleepycat.bind.EntryBinding; import com.sleepycat.bind.serial.SerialBinding; import com.sleepycat.bind.tuple.TupleBinding; import com.sleepycat.db.DatabaseEntry; import com.sleepycat.db.DatabaseException;
Next comes the class declaration and the private data members that we need for this class. Most of these are setting up default values for the program.
Note that two DatabaseEntry
objects are
instantiated here. We will reuse these for every database operation that
this program performs. Also a MyDbEnv
object is
instantiated here. We can do this because its constructor never throws
an exception. See Stored Class Catalog Management with MyDbs for
its implementation details.
Finally, the inventory.txt
and
vendors.txt
file can be found in the GettingStarted
examples directory along with the classes described in this extended
example.
public class ExampleDatabaseLoad { private static String myDbsPath = "./"; private static File inventoryFile = new File("./inventory.txt"); private static File vendorsFile = new File("./vendors.txt"); // DatabaseEntries used for loading records private static DatabaseEntry theKey = new DatabaseEntry(); private static DatabaseEntry theData = new DatabaseEntry(); // Encapsulates the databases. private static MyDbs myDbs = new MyDbs();
Next comes the usage()
and
main()
methods. Notice the exception handling
in the main()
method. This is the only place in the application where we
catch exceptions. For this reason, we must catch
DatabaseException
which is thrown by the
com.sleepycat.db.*
classes.
Also notice the call to MyDbs.close()
in the finally
block. This is the only place in the
application where MyDbs.close()
is called.
MyDbs.close()
is responsible for closing
all open Database
handles for you.
private static void usage() { System.out.println("ExampleDatabaseLoad [-h <database home>]"); System.out.println(" [-s <selections file>]"); System.out.println(" [-v <vendors file>]"); System.exit(-1); } public static void main(String args[]) { ExampleDatabaseLoad edl = new ExampleDatabaseLoad(); try { edl.run(args); } catch (DatabaseException dbe) { System.err.println("ExampleDatabaseLoad: " + dbe.toString()); dbe.printStackTrace(); } catch (Exception e) { System.out.println("Exception: " + e.toString()); e.printStackTrace(); } finally { myDbs.close(); } System.out.println("All done."); }
Next we write the ExampleDatabaseLoad.run()
method. This method is responsible for initializing all objects.
Because our environment and databases are all opened using the
MyDbs.setup()
method, ExampleDatabaseLoad.run()
method is only responsible for calling MyDbs.setup()
and then calling
the ExampleDatabaseLoad
methods that actually load the databases.
private void run(String args[]) throws DatabaseException { // Parse the arguments list parseArgs(args); myDbs.setup(myDbsPath); // path to the environment home System.out.println("loading vendors db."); loadVendorsDb(); System.out.println("loading inventory db."); loadInventoryDb(); }
This next method loads the vendor database. This method
uses serialization to convert the Vendor
object
to a DatabaseEntry
object.
private void loadVendorsDb() throws DatabaseException { // loadFile opens a flat-text file that contains our data // and loads it into a list for us to work with. The integer // parameter represents the number of fields expected in the // file. List vendors = loadFile(vendorsFile, 8); // Now load the data into the database. The vendor's name is the // key, and the data is a Vendor class object. // Need a serial binding for the data EntryBinding dataBinding = new SerialBinding(myDbs.getClassCatalog(), Vendor.class); for (int i = 0; i < vendors.size(); i++) { String[] sArray = (String[])vendors.get(i); Vendor theVendor = new Vendor(); theVendor.setVendorName(sArray[0]); theVendor.setAddress(sArray[1]); theVendor.setCity(sArray[2]); theVendor.setState(sArray[3]); theVendor.setZipcode(sArray[4]); theVendor.setBusinessPhoneNumber(sArray[5]); theVendor.setRepName(sArray[6]); theVendor.setRepPhoneNumber(sArray[7]); // The key is the vendor's name. // ASSUMES THE VENDOR'S NAME IS UNIQUE! String vendorName = theVendor.getVendorName(); try { theKey = new DatabaseEntry(vendorName.getBytes("UTF-8")); } catch (IOException willNeverOccur) {} // Convert the Vendor object to a DatabaseEntry object // using our SerialBinding dataBinding.objectToEntry(theVendor, theData); // Put it in the database. myDbs.getVendorDB().put(null, theKey, theData); } }
Now load the inventory database. This method uses our
custom tuple binding (see InventoryBinding.java) to convert the Inventory
object to a DatabaseEntry
object.
private void loadInventoryDb() throws DatabaseException { // loadFile opens a flat-text file that contains our data // and loads it into a list for us to work with. The integer // parameter represents the number of fields expected in the // file. List inventoryArray = loadFile(inventoryFile, 6); // Now load the data into the database. The item's sku is the // key, and the data is an Inventory class object. // Need a tuple binding for the Inventory class. TupleBinding inventoryBinding = new InventoryBinding(); for (int i = 0; i < inventoryArray.size(); i++) { String[] sArray = (String[])inventoryArray.get(i); String sku = sArray[1]; try { theKey = new DatabaseEntry(sku.getBytes("UTF-8")); } catch (IOException willNeverOccur) {} Inventory theInventory = new Inventory(); theInventory.setItemName(sArray[0]); theInventory.setSku(sArray[1]); Float price = new Float(sArray[2]); theInventory.setVendorPrice(price.floatValue()); Integer vInventory = new Integer(sArray[3]); theInventory.setVendorInventory(vInventory.intValue()); theInventory.setCategory(sArray[4]); theInventory.setVendor(sArray[5]); // Place the Vendor object on the DatabaseEntry object using // our the tuple binding we implemented in // InventoryBinding.java inventoryBinding.objectToEntry(theInventory, theData); // Put it in the database. Note that this causes our // secondary database to be automatically updated for us. myDbs.getInventoryDB().put(null, theKey, theData); } }
The remainder of this application provides utility methods to read a flat text file into an array of strings and parse the command line options:
private static void parseArgs(String args[]) { // Implementation omitted for brevity. } private List loadFile(File theFile, int numFields) { List records = new ArrayList(); // Implementation omitted for brevity. return records; } protected ExampleDatabaseLoad() {} }
From the perspective of this document, these
things are relatively uninteresting. You can see how they are
implemented by looking at ExampleDatabaseLoad.java
in:
DB_INSTALL/examples_java/db/GettingStarted
where DB_INSTALL
is the location where you
placed your DB distribution.